Compression was earlier an important and well-managed part of the clinical routine, but during the past 15-20 y the use has diminished, except for mammography, where it is a prerequisite for having images of high quality and low radiation dose. According to national and European regulations and recommendations, it is important to apply the compression technique to obtain the optimal image quality and radiation dose in common conventional diagnostic examinations. Current experience of compression technique is, however, based on studies carried out a long time ago and with analogue imaging techniques. An anthropomorphic phantom was used to show the importance of compression in conventional X-ray examinations. The patient thicknesses on volunteers with and without compression was measured. This measurement was done to investigate compression potential on patients and to select suitable phantom thicknesses. The X-ray examinations that were included in the study were abdomen overview, lumbar spine and the pelvis. The results from the phantom study showed a large dependency of the kerma-area product value on the phantom thickness. The phantom study suggests that there is a potential for significant reduction of radiation dose to the patient by using compression also with modern X-ray techniques. A dose reduction of up to 50 % or even more may be obtained.

There is great potential to reduce noise and thereby improve image quality by using hybrid or, in particular, model-based iterative reconstruction methods, or to lower radiation dose and maintain image quality.

Computed tomography (CT) is one of the most important modalities in a radiological department. This technique produces images that enables radiological reports with high diagnostic confidence, but may provide an elevated radiation dose to the patient. The radiation dose can be reduced by using advanced image reconstruction algorithms. This study was performed on a Brilliance iCT, equipped with iDose 4 iterative reconstruction and an iterative model-based reconstruction (IMR) method. The purpose was to investigate the effect of reduced slice thickness combined with an IMR method on image quality compared with standard slice thickness with iDose 4 reconstruction. The results of objective and subjective image quality evaluations showed that a thinner slice combined with IMR can improve the image quality and reduce partial volume artefacts compared with the standard slice thickness with iDose 4 . In conclusion, IMR enables reduction of the slice thickness while maintaining or even improving image quality versus iDose 4 .